Electroacoustic transducer with built in transducer circuit

ABSTRACT

In an electroacoustic transducer ( 1 ), an annular shaped magnet system ( 14 ) is provided, enclosing an inner space ( 22 ), in which inner space ( 22 ) an integrated circuit ( 31 ) is accommodated, with the aid of which integrated circuit ( 31 ) an electrical signal to be sent to a moving coil ( 29 ) of transducer ( 1 ) can be amplified.

The invention relates to an electroacoustic transducer with a transduceraxis and comprising a membrane, which membrane is arranged perpendicularto the transducer axis so as to be oscillatory, and comprising a magnetsystem, which magnet system is equipped with two magnet-systemcomponents, which magnet-system components bound an air gap, andcomprising a moving coil, which moving coil is, in part, arranged in theair gap and is connected to the membrane, and comprising a circuitmodule, which circuit module is equipped with a circuit frame and atleast one circuit component of a transducer circuit, mounted on thecircuit frame.

An electroacoustic transducer in accordance with the generic type citedin the first paragraph above is known from patent document U.S. Pat. No.6,243,472 B1. In the known transducer, a multiplicity of circuitcomponents are provided on the board-shaped circuit frame of the circuitmodule, wherein these circuit components are all mounted on the circuitframe carrier surface that faces away from the membrane. The result ofthis is that, parallel with the direction of the transducer axis, thecircuit components protrude from the circuit frame carrier surface thatfaces away from the membrane and therefore occupy a space, which leadsto an increase in the space requirement of the known transducer in thedirection of the transducer axis. Although such an increase in spacerequirement in the direction of the transducer axis does not occur in afurther electroacoustic transducer known from cited patent document U.S.Pat. No. 6,243,472 B1 because, in this further known transducer thecircuit module is accommodated within the magnet system, however, inthis further known transducer, no repairs can be made to the circuitmodule and no exchanging of the circuit module can take place in theevent of a non-operational circuit module—which may be caused by e.g. adefective circuit component—so the entire electroacoustic transducerthen has to be replaced.

It is an object of the invention to eliminate the above-mentioneddisadvantageous circumstances and to realize an improved electroacoustictransducer.

To achieve the above-mentioned object, features in accordance with theinvention are provided in an electroacoustic transducer in accordancewith the invention, so that an electroacoustic transducer in accordancewith the invention may be characterized in the following manner, namely:

Electroacoustic transducer with a transducer axis and comprising amembrane, which membrane is arranged perpendicular to the transduceraxis so as to be oscillatory, and comprising a magnet system, whichmagnet system is equipped with two magnet-system components bounding anair gap, and comprising a moving coil, which moving coil is, in part,arranged in the air gap and is connected to the membrane, and comprisinga circuit module, which circuit module is equipped with a circuit frameand at least one circuit component of a transducer circuit, mounted onthe circuit frame, wherein the magnet system is arranged in an annularshape and encloses an inner space, which inner space is accessible fromoutside the magnet system during production of the transducer and beforethe circuit module is mounted, and wherein the at least one circuitcomponent is arranged on a first carrier surface of the circuit framewhich first carrier surface faces the membrane, and in the inner spaceof the magnet system.

By providing the features in accordance with the invention, firstly, anespecially space-saving design of an electroacoustic transducer with abuilt-in transducer circuit is enabled in a structurally simple manner,since the board-shaped circuit frame may be of an extremely thin design,and the at least one circuit component mounted on the circuit frame isaccommodated within the inner space of the magnet system and thereforetakes up no additional space parallel to the transducer axis, andsecondly, it is advantageously achieved that the circuit module isaccessible easily and simply even after the completion of theelectroacoustic transducer, and, in the event that operation isunsatisfactory, may be replaced in an easy and simple way.

In an electroacoustic transducer in accordance with the invention,multiple discrete circuit components may be provided on the circuitframe to create a transducer circuit. A transducer circuit of this kindmay also be realized in thin-film technology. It has, however, provedvery advantageous if just a single circuit component is provided, whichtakes the form of an integrated circuit connected to the circuit frame,which integrated circuit forms the transducer circuit. An especiallysmall, space-saving solution can be realized as a result.

In an embodiment with an integrated circuit, it has further proved veryadvantageous if, in addition, the features as claimed in claim 3 areprovided. A solution of this kind is advantageous in respect of thesimplest possible embodiment of the electrically conductive connectionbetween the moving coil and the transducer circuit.

In an electroacoustic transducer in accordance with the invention,connecting contacts running parallel with one another in the form ofspots or strips may be provided on a second carrier surface of thecircuit frame which second carrier surface facing away from themembrane. It has, however, proved very advantageous if four connectingcontacts, each having the shape of an annular sector, are provided on asecond carrier surface of the circuit frame which second carrier surfacefaces away from the membrane. An embodiment of this kind has provedespecially advantageous in practice.

The circuit module may be secured with, for example, at least one screw.It has, however, proved especially advantageous if the circuit module isdesigned to be removable without a separate tool. To this end, forexample, a latching connection or a bayonet connection may be providedbetween the circuit module and another component of the transducer. Aninterference fit, which may be extensive to a greater or lesser extent,may also be provided between the circuit module and another component ofthe transducer.

The above aspects and further aspects of the invention are explainedbelow.

The invention will be further described with reference to examples ofembodiments shown in the drawings, to which, however, the invention isnot restricted.

FIG. 1 shows, in cross-section, an electroacoustic transducer inaccordance with a first embodiment of the invention, which transducer isprovided with a circuit module.

FIG. 2 shows, in an oblique view from behind, the transducer inaccordance with FIG. 1 without the circuit module.

FIG. 3 shows, in an oblique view from behind, the circuit module of thetransducer in accordance with FIG. 1.

FIG. 4 shows, in an oblique view from in front, the circuit module ofthe transducer in accordance with FIG. 1.

FIG. 1 shows an electroacoustic transducer 1, which in this case is aloudspeaker 1. Transducer 1 is essentially centrally symmetrical indesign, and has a transducer axis 2.

The transducer 1 has a pot-shaped housing 3, which is made of metal andwhich is equipped with a base wall 4 and a side wall 5, wherein the basewall 4 is provided with a circular elevation 6, in which circularelevation 6 sound transmission openings are provided (not shown) andwherein four strip-shaped lugs 7, running in radial directions inrelation to transducer axis 2, protrude from side wall 5, with the aidof which lugs 7 the components of transducer 1 accommodated in housing 3are secured in their axial positions. More than four lugs 7 of this kindmay also be provided. The radial positions of the components oftransducer 1 which are accommodated in housing 3 are defined with theaid of side wall 5. In the direction of transducer axis 2 and in thearea of transducer axis 2, the pot-shaped housing 3 has a height of 3.2mm. The diameter of housing 3 in the directions running perpendicular tothe direction of transducer axis 2 is 13.2 mm. In this case, therefore,transducer 1 is of an especially small design. Transducer 1 is providedfor use in e.g. a mobile telephone or in similar telecommunicationsapparatuses, which apparatuses need to be especially small, so thecomponents used therein, like transducer 1, also need to be especiallysmall and take up little space. Consequently, it is advantageous inrelation to a transducer 1 of this kind if its dimensions are smaller incomparison with known transducers, even if by only a few tenths of amillimeter.

The transducer 1 contains a membrane 8, which is essentially U-shaped inits peripheral area 9, wherein the U-shaped peripheral area 9 isconnected to a ring 10, which ring 10 is connected to membrane 8 whenmembrane 8 is produced, and which ring 10 serves for transport purposesand also for assembly purposes. When transducer 1 is produced, ring 10,including the membrane 8 which is connected to it, is inserted intohousing 3 in parallel with, the direction of transducer axis 2, whereinthe lugs 7 have, of course, not yet been bent over and extend in adirection running essentially parallel with transducer axis 2. Membrane8 has an intermediate area 11 adjacent to U-shaped peripheral area 9,and an annular securing area 12 adjacent to intermediate area 11, and acentral area 13 located within securing area 12, which central area 13serves for sound generation. To this end, membrane 8 as a whole isarranged perpendicular to transducer axis 2 so as to be oscillatory.

The transducer 1 is further equipped with a magnet system 14. Magnetsystem 14 comprises a permanent magnet 15 and an annular first yoke 16,which yoke 16 is located tight against permanent magnet 15, and a secondyoke 17, having an L-shaped cross-sectional shape, of which second yoke17, one disk-shaped first section 18 is likewise located tight againstpermanent magnet 15, and a hollow-cylindrical second section 19protrudes from first section 18 parallel with transducer axis 2. Whentransducer 1 is produced, firstly first yoke 16, then permanent magnet15 and then second yoke 17 are inserted into housing 3 parallel with thedirection of transducer axis 2. Once the three components 16, 15 and 17of the magnet system have been inserted, lugs 7 of housing 3 are bentover into their positions as shown in FIG. 1 and FIG. 2, as a result ofwhich membrane 8 and magnet system 14 are fixed. An air gap 20 is formedbetween the free end of second section 19 of second yoke 17 and theinner edge of first yoke 16, which air gap 20 is bounded by the twocomponents of the magnet system, namely first yoke 16 and second yoke17. Magnet system 14 has a boundary surface 21, which faces away frommembrane 8 and bounds magnet system 14 externally, and which boundarysurface 21 is formed by an annular surface of first section 18 of secondyoke 17.

As can be seen from FIG. 1 and FIG. 2, magnet system 14 advantageouslytakes an annular shape in the present case. Magnet system 14 encloses aninner space 22, which inner space 22, when magnet system 14 is produced,is accessible from outside magnet system 14 over its entire extent,located perpendicular to transducer axis 2, before circuit module 23—thedesign of which will be described below—is fitted, and which inner space22 is permeated by transducer axis 2.

Fixed in inner space 22 is a contact carrier 24, which contact carrier24 is made of plastic and is provided to hold two moving-coil contacts25, only one of which moving-coil contacts 25 is visible in FIG. 1 owingto the sectional view. Moving-coil contacts 25 are connected to acontact carrier 24 by means of extrusion. Each moving-coil contact 25 isequipped with a U-shaped section 26, between the two legs of which anend 27 of a moving-coil wire is clamped. Each moving-coil contact 25 isequipped with an L-shaped section 28, which protrudes from a leg ofU-shaped section 26.

The transducer 1 contains a moving coil 29, which moving coil 29 ispartly arranged in air gap 20 and is connected to membrane 8 in itssecuring area 12 with the aid of an adhesive connection, which is notshown. Moving coil 29 interacts with magnet system 14, wherein anelectrical signal representing a signal to be reproduced acoustically issent to moving coil 29, as a result of which moving coil 29 is caused tooscillate, which results in membrane 8 bringing about the signal to bereproduced acoustically. The electrical signal sent to moving coil 29must be amplified and, if applicable, its signal waveform must beinfluenced, before being sent to moving coil 29. A transducer circuit,which is designed to undertake the necessary signal influencing,especially to amplify the signal, is required for this purpose.

In the transducer 1, this transducer circuit is directly connected totransducer 1. The already-mentioned circuit module 23 is provided in thetransducer 1 for this purpose. The circuit module 23 is equipped with aboard-shaped circuit frame 30, which circuit frame 30 is arrangedadjacent to the boundary surface 21 of the annular magnet system 14 inthe axial direction. Provided on and attached to board-shaped circuitframe 30 in the present case is just a single circuit component 31,which is formed by an integrated circuit 31 connected to circuit frame30, which integrated circuit 31 is indicated only schematically in FIG.1, and which integrated circuit 31 forms the transducer circuit.Integrated circuit 31 is hereby arranged in an advantageous manner on afirst carrier surface 32 of circuit frame 30 that faces membrane 8. Thisgives rise to the fact that integrated circuit 31 is arranged in theinner space 22 of magnet system 14, as a result of which the greatadvantage is achieved that, for accommodating integrated circuit 31,advantage is taken of the space that is available anyway in inner space22, so that no additional space is required for accommodating integratedcircuit 31, which is advantageous in respect of the lowest possibleheight of transducer 1, including the transducer circuit. Integratedcircuit 31 is hereby embedded in an essentially pot-shaped plasticjacket 33. Protruding from plastic jacket 33 are two connection contacts34, connected to this plastic jacket 33 by extrusion, each of whichconnection contacts 34 is connected to a moving-coil contact 25 to beelectrically conductive, wherein the electrically conductive connectionis realized, in each case, between a connection contact 34 and anL-shaped section 28 of a moving-coil contact 25. Each of the twoconnection contacts 34 is connected to a (not shown) terminal ofintegrated circuit 31. In this case, circuit frame 30 takes the form ofa small printed circuit board, to which plastic jacket 33 is connected.However, circuit frame 30 and plastic jacket 33 may also comprise onepiece, wherein circuit frame 30 is then also made of plastic, as aresult of which an especially simple, advantageous embodiment isachieved.

As can be seen in FIG. 3, four terminal contacts 36, each taking theform of an annular sector, are provided on a second carrier surface 35of circuit frame 30 that faces away from membrane 8. Two of theseterminal contacts 36 serve for sending the electrical signal to bereproduced as an acoustic signal. Two other of these terminal contacts36 serve for sending a direct supply voltage for the integrated circuit31.

In the present case, circuit module 23 is secured with the aid of alatching connection, not shown in the Figures. This latching connectionis realized between the contact carrier 24 and the plastic jacket 33.The latching connection may, however, also be provided between othercomponents of transducer 1, e.g. between the second yoke 17 and circuitframe 30. By virtue of the securing of circuit module 23 with the aid ofa latching connection, circuit module 23 can be removed from theremainder of transducer 1 without separate tools. Circuit module 23 isthereby of a design that can be removed without separate tools. Circuitmodule 23 may, however, also be secured with the aid of quick-releasesnap connection or bayonet connection. Circuit module 23 may also besecured with the aid of e.g. spot-shaped adhesive connections orspot-shaped weld connections.

With the transducer 1, it is achieved in an especially advantageousmanner that, firstly, only a very small additional space requirement isnecessary in the direction of transducer axis 2 for accommodatingintegrated circuit 31, namely the space necessary for the board-shapedcircuit frame 30, which is, however, only a few tenths of a millimeter,and that, secondly, circuit module 23 is accessible simply and easilyeven after the completion of transducer 1, and can be replaced simplyand easily in the event that circuit module 23 is not operatingsatisfactorily.

In a modification of the transducer 1 in accordance with FIGS. 1 to 4,no circuit frame extending as far as side wall 5 of housing 3 isprovided; instead, circuit frame 30 has an outside diameter that is onlyequal to the inside diameter of the inner space 22, and plastic jacket33, together with circuit frame 30, occupies only a height such that thesecond carrier surface 35 of circuit frame 30 that faces away frommembrane 8 is in alignment with boundary surface 21 of magnet system 14,or even lies somewhat offset into the inner space in relation toboundary surface 21 in the axial direction, so that, in this case too,circuit frame 30 is arranged adjacent to boundary surface 21 of magnetsystem 14, specifically adjacent essentially in the radial direction. Asa result, there is no additional space requirement whatever in thedirection of transducer axis 2 for accommodating the circuit module 23,which contains integrated circuit 31. In this modification of transducer1, circuit frame 30 may take the form of a base wall of the plasticjacket 33.

As regards circuit module 23, it should also be mentioned that circuitmodule 23 is of an SMD-capable (Surface Mount Device) design andtherefore can be connected by an SMD method to a PCB (Printed CircuitBoard) of a mobile telephone or a similar apparatus. Circuit module 23thereby forms an SMD-capable adapter for transducer 1, wherein thisadapter can be connected, or cannot be connected, to the remainder oftransducer 1, depending on client request or application case.

It should be further mentioned that an intermediate layer may also beprovided between the boundary surface 21 of magnet system 14 that facesaway from membrane 8 and the first carrier surface 32 of circuit frame30 that faces membrane 8, which intermediate layer is designed toachieve an especially good thermal transmission between the circuitframe 30 and the second yoke 17 of magnet system 14.

As regards transducer 1, it should also be mentioned that it is alsopossible for no circuit module 23 to be supplied for transducer 1, i.e.to supply the client with a transducer 1 without a circuit module 23 ofthis kind for installation in a mobile telephone or a similar apparatus,wherein a transducer 1 of this kind supplied without a circuit module 23then has to be supplied with the electrical signal to be reproducedacoustically from a transducer circuit external to transducer 1, whereinthis external transducer circuit is directly connected to the L-shapedsections 28 of the two moving-coil contacts 25.

It may be mentioned that an electroacoustic transducer in accordancewith the invention may also be a microphone.

1. An electroacoustic transducer with a transducer axis and comprising amembrane, which membrane is arranged perpendicular to the transduceraxis so as to be oscillatory, wherein the membrane includes anintermediate area adjacent to a U-shaped peripheral area and an annularsecuring area adjacent to the intermediate area, and a central arealocated within the annular securing area, said central area serves forsound generation, and comprising a magnet system, which magnet system isequipped with two magnet-system components, which magnet-systemcomponents bound an air gap, and comprising a moving coil, which movingcoil is, in part, arranged in the air gap and is connected to themembrane, and comprising a circuit module, which circuit module isequipped with a circuit frame and one single circuit component whichforms a transducer circuit, the one single circuit component mounted onthe circuit frame, the one single circuit component being an integratedcircuit connected to the circuit frame, wherein the magnet system isarranged in an annular shape and encloses an inner space, which innerspace is accessible from outside the magnet system during production ofthe transducer and before the circuit module is mounted, and wherein theat least one circuit component is arranged on a first carrier surface ofthe circuit frame which first carrier surface faces the membrane, and inthe inner space of the magnet system.
 2. An electroacoustic transduceras claimed in claim 1, wherein the integrated circuit is embedded in aplastic jacket and wherein two connection contacts are provided on theplastic jacket, each of which connection contacts is connected to amoving-coil contact.
 3. An electroacoustic transducer as claimed inclaim 1, wherein four connecting contacts, each having the shape of anannular sector, are provided on a second carrier surface of the circuitframe which second carrier surface faces away from the membrane.
 4. Anelectroacoustic transducer as claimed in claim 1, wherein the circuitmodule is of a design that can be removed without separate tools.
 5. Anelectroacoustic transducer as claimed in claim 1, wherein the transducerhas a pot-shaped housing wherein, in the direction of the transduceraxis, its height has a value between 2.0 mm and 5.0 mm and its diameterperpendicular to the direction of the transducer axis has a valuebetween 6.0 mm and 20.0 mm.